Percussion tool with replaceable point



Aug. 15, 1967 5.5. ERICSSON PERCUSSION TOOL WITH REPLACEABLE POINT Filed Aug. 2, 1965 SAMUEL $1 ER/CSSON N VE /V T 0/? BUCKHOR/V, BLORE, KLAROU/ST a SPAR/(MAN ATTORNEYS United States Patent 3,336,081 PERCUSSION TOOL WITH REPLACEABLE POINT Samuel S. Ericsson, Lake Oswego, Oreg. (3320 SE. 50th Ave., Portland, Oreg. 97206) Filed Aug. 2, 1965, Ser. No. 476,480 1 Claim. (Cl. 299-91) ABSTRACT OF THE DISCLOSURE This invention relates to impact or percussion-driven tools such as are used with pneumatically or electrically powered hammers for breaking up pavement, concrete and other hard materials and, more particularly, to such a tool having a replaceable point.

Percussion tools have been available with replaceable points. One such tool is disclosed in Coski Patent No. 3,027,953. Such tools have been formed, however, with a replaceable point having a maximum diameter greater than the diameter of the shank. A replaceable point so constructed will often catch on the concrete or pavement being broken up, thereby to become separated from the shank or otherwise to cause the operator inconvenience and trouble.

It is thus an object of the present invention to provide a percussion tool having a replaceable point that will not come 01f in use.

It is a further object of the present invention to provide such a tool with a replaceable point that can be loosened and replaced quickly and easily, when desired by the operator.

' The percussion tool of the present invention has a shank and a replaceable sharpened point. The shank, however, instead of being of constant cross section, gradually increases in diameter toward the end which is adapted to receive the sharpened point. This enlarged diameter forms a shoulder near the end of the shank, and the shank thereafter tapers inwardly from the shoulder. The sharpened point has a corresponding inwardly recessed tapered surface, so that it can engage with the tapered surface on the shank. By virtue of the shoulder formed on the shank, the maximum diameter of the sharpened point is substantially equal to the maximum diameter of the shank. Thus, I have minimized the possibility of the sharpened point catching on the work, or otherwise causing trouble by reason of a lateral protrusion.

It has been found that if the shank is tapered at an angle of about degrees with respect to its longitudinal axis, the impact of the percussion force is transmitted satisfactorily to the sharpened point, yet the latter is easily and quickly removed from the shank whenever necessary. The inwardly recessed surface of the sharpened point is also desirably made to taper at an angle of about 5 degrees with respect to the longitudinal axis of the tool, thereby to correspond with the taper on the shank.

Other features and advantages of the present invention will become apparent from the following description of a typical embodiment, wherein like numerals refer to like parts, and wherein;

FIG. 1 is an exploded perspective view of the percussion tool of the present invention showing the shank and sharpened point disassembled;

FIG. 2 is an exploded side view of the work-entering end of the tool shown in FIG. 1 with parts disassembled, and with the sharpened point shown partly in section; and

FIG. 3 is a side view of the work entering end of the tool showing the parts assembled together.

Referring to the drawings, the percussion tool 10 of the invention has a shank 11, the upper end 12 of which is adapted to be held in the jaws of a pneumatically or electrically powered hammer (not shown). The end 12 is formed to fit the jaws of the hammer. As shown it has a hexagonal shape, although it may be of any suitable shape to engage in the hammer, and terminates in a collar 13. Between the collar 13 and the end 20 of the shank adapted to receive the sharpened point, the shank has a body portion 14 of circular cross-section, as shown. The cross-section of the body portion 14 is of constant diameter for a portion of the length of the shank from the collar 13, but thereafter gradually increases in diameter to a shoulder 15 of maximum diameter adjacent the point receiving end 20. For example, if the body portion 14 of the shank has a diameter of 1% inches in its constant diameter portion, such diameter may be enlarged to 1 inches at the shoulder 15. The diameter of the shank is thereafter sharply reduced to form a neck 16, joining the end 20 and shoulder 15.

The point receiving end 20 is formed with a frustoconical surface 21 that preferably defines a small acute, included angle of about 5 degrees with respect to the longitudinal axis AA of the shank. The inwardly tapered surface 21 of the shank is shown terminating in a blunt surface 22, which is perpendicular to the longitudinal axis AA, although the surface 22 could be rounded if desired.

A sharpened point 25 is adapted to fit on the tapered surface 21 of the shank 11. The point 25 has an outer diameter at its upper end substantially equal to the diameter of the shoulder 15 and is formed with an opening 26 defined in part by a frusto-conical wall 27, which has a complementary taper of about 5 degrees also with respect to the longitudinal axis A-A of the tool. The open ing 26 in the point 25 terminates in a convex curved surface 30.

The opening 26 and shank end 20 are so dimensioned that the shank end 20 is received within the opening 26 without bottoming out, which is important, of course, both from the standpoint of transmitting forces from the shank to the point and also in retaining the point upon the shank. In this regard, it should be noted that the -5 degree taper permits the percussive force to be transmitted by the shank to the point, yet the point can be easily and quickly removed from the shank as desired. The wall 27 is made sufiiciently thick to withstand the forces expected in use. The point terminates in a conventional sharpened cutting point 29.

When the sharpened point 25 is placed in position on the tapered end of the shank 11 and interfittingly engages therewith, it will be seen from FIG. 3 that the upper end of the wall 28 of the point 25 does not protrude laterally of the shank, and there is a minimum of likelihood of the point catching on the Work.

The shank and point 25 may be formed of any suitable steel, capable of being normalized and heat-treated to a suitable hardness.

In the foregoing description, the invention has been described with reference to a certain particular embodiment, although it is to be understood that the specific details shown are merely illustrative and that the invention may be carried out in other ways without departing from the true spirit and scope of the appended claim.

I claim:

A replaceable point type of percussion tool, comprismg:

3 a sharpened point and a shank,

said shank having one end adapted to be struck, the other end being adapted to receive said sharpened point, said shank gradually increasing in diameter from said one end toward said other end to provide a shoulder of maximum diameter intermediate said ends; said shank tapering inwardly from said shoulder to said other end at a small acute angle with the longitudinal axis of said shank to define thereby a point engaging portion, said sharpened point having an opening having an inwardly recessed frusto-conical surface tapering at a complementary angle to said small acute angle and terminating in a convex curved surface, said point 4. engaging portion of said shank and said opening in said sharpened point being so dimensioned that said opening receives said shank without permitting said shank to bottom in said opening, the maximum diameter of said sharpened point being substantially equal to the maximum diameter of said shoulder on said shank.

References Cited UNITED STATES PATENTS 2,454,771 11/1948 Carr 175419 FOREIGN PATENTS 867,381 2/1953 Germany.

ERNEST R. PURSER, Primary Examiner. 

